1. Field of the Invention
This invention relates to a throttle control apparatus attached to an engine and having two, main and sub, throttle actuators. To be more specific, this invention relates to an electronic throttle control apparatus, and particularly relates to an electronic throttle control apparatus for rapidly detecting a failure occurring in a throttle control system by using the modern control theory.
2. Description of the Relates Art
An apparatus for controlling the opening of a throttle valve by electronic control is disclosed in U.S. Pat. No. 4,603,675. This prior art apparatus has a single valve mechanism, and if the valve mechanism becomes unable to move, it follows that the engine increases in the number of revolutions. In order to prevent this problem, this U.S. patent suggests various failure diagnostic methods. However, since in these diagnostic methods, diagnosis is made according to stationary or quasi-stationary signals, these methods are incapable of quick detection of unforeseen accidents. In other words, if a comparison is made between the accelerator position and the throttle valve position, since there is a deviation due to a dynamic delay between the two positions, it is impossible to make a distinction between this deviation and a deviation resulting from a failure, making it impossible to watch out for a failure at all times. Therefore, when an unexpected failure takes place, the failure cannot be detected until an abnormal motion caused by the failure settles down, so that it is relatively difficult to prevent the engine speed from increasing.